This invention relates to an electric chain block having a torque limiter and a mechanical brake in a reduction gear assembly.
An electric chain block having a torque limiter and a mechanical brake is known as disclosed Japanese Patent Application Publication No. 38,378/79. In such an electric chain block, a driving shaft connected to a rotating shaft of an electric motor is integrally formed with a driving gear, and a hollow driven shaft having a load sheave thereon is rotatably fitted on the driving shaft. Moreover, a torque limiter having an annular driven gear and a mechanical brake are arranged in series side by side on the hollow driven shaft. An intermediate driven shaft is located in parallel with the driving shaft and is provided thereon with an intermediate driven gear and an intermediate drive gear which are in mesh with the driving gear and the annular driven gear, respectively.
With this electric chain block, however, the torque limiter cannot be adjusted to change its transmitting torque from outside of the chain block after it has been assembled. Moreover, this chain block has a disadvantage of an unduly long driving shaft which makes the chain block bulky.
Moreover, an electric chain block including a reduction gear assembly having a torque limiter and a mechanical brake has been disclosed in Japanese Patent Application Publication No. 42,937/78. With this chain block, an intermediate shaft and a brake restraining member must be worked to from screw threads with high accuracy. This in turn increases the cost of manufacturing. Similar to the first mentioned prior art, moveover, transmission torque of the torque limiter cannot be adjusted from outside of a gear box after assembling.